Substrate for magnetic recording medium, magnetic recording medium, and magnetic recording and reproducing apparatus

ABSTRACT

In an example magnetic recording medium substrate, a plurality of recording tracks are formed on a substrate, each recording track being formed of a magnetic material. Non-recording sections are formed on the substrate, each non-recording section separating adjacent recording tracks. Each recording track includes a plurality of recording sections and connecting sections for connecting the recording sections adjacent thereto in a track longitudinal direction, and each connecting section has a cross-sectional area in a track width direction that is smaller than a cross-sectional area in a track width direction of adjacent recording sections.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 12/503,458,filed Jul. 15, 2009, which is a divisional of application Ser. No.11/397,892, filed on Apr. 5, 2006, now, U.S. Pat. No. 7,760,467, whichis based upon and claims the benefit of priority from prior JapanesePatent Application No. 2005-254336, filed on Sep. 2, 2005 in Japan. Theentire contents of each of these applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an uneven substrate for manufacturing amagnetic recording medium capable of performing high-density recording,a method of manufacturing such an uneven substrate, a magnetic recordingmedium and a method of manufacturing a magnetic recording medium, and amagnetic recording apparatus including such a magnetic recording medium.

2. Background Art

A hard disk drive is a recording apparatus including a housing and amagnetic disk provided within the housing. The magnetic disk is formedby depositing a film of a magnetic material (magnetic film) on a glasssubstrate. A magnetic film is composed of fine particles each havingmagnetic domains.

Between records, noise is generated in accordance with the particlesize. In order to achieve high density recording, the size of magneticdomains of a magnetic recording medium, which is the informationrecording unit, should be made smaller. However, if the size of magneticdomains is made too small, a thermal fluctuation problem occurs, whichmakes it difficult to maintain records at a room temperature.Accordingly, at present, two kinds of magnetic recording media areproposed, in which a recording layer composed of a generally-usedcontinuous magnetic material is cut at portions unable to performmagnetic recording, thereby improving a recording efficiency whilemaintaining the size of magnetic domains.

In one of the aforementioned two kinds of magnetic recording media, adiscrete magnetic recording medium, adjacent recording tracks in amagnetic disk are separated by a non-recording section, therebydecreasing the track pitch while maintaining the track position data(for example, Japanese Patent Laid-Open Publication No. 2003-16621). Itis possible to prevent the interference between recording tracks byphysically separating the magnetism of recording tracks of a magneticmaterial and eliminating the effect of the leakage magnetic field of arecording and reproducing head, thereby narrowing the tracks.

In the other kind of magnetic recording medium, a patterned medium, themagnetic particles are regularly arranged in a nonmagnetic basematerial, and the size of each magnetic particle is regarded as the sizeof the recording magnetic domain (for example, Japanese Patent Laid-OpenPublication No. 2000-251236). In this manner, it is possible to fix therecording positions and to solve the thermal fluctuation problem at thesame time. However, highly accurate processing steps are required toregularly arrange magnetic particles having a continuous magneticproperty and to process a magnetic material. In particular, thedegradation in the size and the direction of the vertical magneticanisotropy of a recording film is a significant problem. Furthermore,although the head flying height of a recording and reproducing headshould be lowered in order to improve the recording efficiency, it isdifficult to decrease the flying height, and a number of smoothing stepsare required when a patterned medium, which has a number of projectionsand depressions, is used.

When a discrete magnetic recording medium is used, recording isperformed within a recording track having a predetermined width.However, the recording position tends to shift because of a shift in thetrack direction of the recording and reproducing head within a track.Thus, there is a problem in that the S/N ratio of the recording andreproducing is degraded.

When a patterned medium is used, a good S/N ratio can be obtained sincethe recording sections are completely separated to always fix therecording positions. However, because the recording sections areseparated, there is a problem in that the area that can be used forrecording is small, and the intensity of a reproduction signal is low.

SUMMARY OF THE INVENTION

The present invention is proposed in consideration of the aforementionedcircumstances, and it is an object of the present invention to provide amagnetic recording medium with a good recording and reproducing S/Nratio and a high reproduction signal intensity, the magnetic recordingmedium being capable of high-density recording. It is also an object ofthe present invention to provide a magnetic recording medium substratefor manufacturing such a magnetic recording medium, and a magneticrecording apparatus.

A magnetic recording medium according to a first aspect of the presentinvention includes: a plurality of recording tracks formed on asubstrate, each recording track being formed of a magnetic material; andnon-recording sections formed on the substrate, each non-recordingsection separating adjacent recording tracks, each recording trackincluding a plurality of recording sections and connecting sections forconnecting the recording sections adjacent thereto in a tracklongitudinal direction, and each connecting section having across-sectional area in a track width direction that is smaller than across-sectional area in a track width direction of adjacent recordingsections.

A magnetic recording medium substrate according to a second aspect ofthe present invention includes: a plurality of protruded portions formedon a substrate, each recording track being in a track shape; anddepressed portions formed on the substrate, each depressed portionseparating adjacent protruded portions, each protruded portion includinga plurality of first portions and second portions for connecting thefirst portions adjacent thereto in a track longitudinal direction, andeach second portion having a cross-sectional area in a track widthdirection that is smaller than a cross-sectional area in a track widthdirection of adjacent first portions.

A magnetic recording medium according to a third aspect of the presentinvention includes: the aforementioned magnetic recording mediumsubstrate; and a magnetic film formed on the magnetic recording mediumsubstrate.

The magnetic recording medium according a fourth aspect of the presentinvention includes: the aforementioned magnetic recording medium; and ahead relatively moves above the magnetic recording medium when arecording or reproducing operation is performed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a magnetic recording medium according to afirst embodiment of the present invention.

FIG. 2 is a perspective view of a recording track of the magneticrecording medium according to the first embodiment.

FIG. 3 is a perspective view of a recording track of a magneticrecording medium according to a first modification of the firstembodiment.

FIG. 4 is a sectional view of the magnetic recording medium of the firstembodiment in a track width direction.

FIG. 5 is a sectional view of a magnetic recording medium according to asecond modification of the first embodiment in a track width direction.

FIG. 6 schematically shows an MFM image of the magnetic recording mediumaccording to the first embodiment.

FIG. 7 schematically shows an MFM image of a discrete medium.

FIG. 8 schematically shows an MFM image of a patterned medium.

FIG. 9 shows a reproduction signal waveform of the magnetic recordingmedium according to the first embodiment.

FIG. 10 shows a reproduction signal waveform of a patterned medium.

FIG. 11 shows a reproduction signal waveform of a discrete medium.

FIG. 12 is a plan view of a magnetic recording medium substrateaccording to a second embodiment of the present invention.

FIG. 13 is a sectional view of the magnetic recording medium substrateaccording to the second embodiment taken along line A-A of FIG. 12.

FIG. 14 is a sectional view of a magnetic recording medium in a trackwidth direction, the magnetic recording medium being manufactured usingthe magnetic recording medium substrate according to the secondembodiment.

FIG. 15 is a sectional view of a magnetic recording medium in a trackwidth direction, the magnetic recording medium being manufactured usingthe magnetic recording medium substrate according to the secondembodiment.

FIG. 16 is a sectional view of a magnetic recording medium in a trackwidth direction, the magnetic recording medium being manufactured usingthe magnetic recording medium substrate according to the secondembodiment.

FIG. 17 is a sectional view of a magnetic recording medium in a trackwidth direction, the magnetic recording medium being manufactured usingthe magnetic recording medium substrate according to the secondembodiment.

FIG. 18 is a perspective view showing a schematic structure of a mainpart of a magnetic recording and reproducing apparatus.

FIG. 19 is an enlarged perspective view of a magnetic head assembly at aportion extending from an actuator arm viewed from the disk side.

FIG. 20 shows an exposure pattern of portions corresponding to recordingsections and connecting sections in a case where an imprint stamper ismanufactured.

FIGS. 21A to 21G are sectional views showing steps of a process ofmanufacturing an imprint stamper.

FIG. 22 shows a first example of an exposure pattern when an imprintstamper is manufactured.

FIG. 23 shows a second example of an exposure pattern when an imprintstamper is manufactured.

FIG. 24 is a drawing for explaining a method of manufacturing an imprintstamper.

FIG. 25 is a plan view of an imprint stamper manufactured by the methodshown in FIG. 24.

FIGS. 26A to 26D are sectional views showing steps of a process ofmanufacturing a magnetic recording medium according to Example 1 of thepresent invention.

FIGS. 27A to 27D are sectional views showing steps of the process ofmanufacturing a magnetic recording medium according to Example 1 of thepresent invention.

FIGS. 28A to 28D are sectional views showing steps of a process ofmanufacturing a magnetic recording medium according to Example 2 of thepresent invention.

FIGS. 29A to 29D are sectional views showing steps of a process ofmanufacturing a magnetic recording medium using a magnetic recordingmedium substrate according to Example 2 of the present invention.

FIGS. 30A to 30C are perspective views showing steps of a process ofmanufacturing a magnetic recording medium according to Example 3 of thepresent invention.

FIGS. 31A to 31D are perspective views showing steps of the process ofmanufacturing a magnetic recording medium according to Example 3 of thepresent invention.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described below withreference to the accompanying drawings.

First Embodiment

FIG. 1 shows a plan view of a magnetic recording medium according to afirst embodiment of the present invention. The magnetic recording mediumin this embodiment includes a plurality of recording tracks 2 formed ofa magnetic material on a substrate, which is not shown, andnon-recording sections 4 each separating adjacent recording tracks 2.Each recording track 2 includes recording sections 2 a, in whichrecorded information is stored, and connecting sections 2 b eachconnecting adjacent recording sections 2 a. Pairs each including arecording section 2 a and a connecting section 2 b are disposed atregular intervals in a longitudinal direction of the track. Onerecording section 2 a stores a magnetic information item correspondingto a data item “0” or “1”.

FIG. 2 shows a perspective view of one recording track 2. As shown inFIG. 2, the cross sectional area in a direction perpendicular to thetrack longitudinal direction, i.e., the track width direction, of theconnecting section 2 b decreases as the distance from one of theadjacent recording sections 2 a increases, and increases as the distanceto the other recording section 2 a decreases. Thus, the cross sectionalarea becomes the smallest at a substantially central portion of theconnecting section 2 b. Furthermore, the greatest cross sectional areain the track width direction of the connecting section 2 b is adjustedto be substantially the same as the smallest cross sectional area of therecording section 2 a. That is to say, the connecting section 2 bincludes a portion for which the cross sectional area is smaller thanthe cross sectional area of the recording section 2 a. In thisembodiment, the smallest cross sectional area of the connecting section2 b is not “0”. In the other embodiments described later, the smallestcross sectional area can be “0”. Furthermore, in this embodiment, thesmallest cross sectional area of the connecting section 2 b is at asubstantially central portion of the connecting section 2 b but can notbe at central portion of the connecting section 2 b. Where else, thecross-sectional area in the track width direction of each connectingsection 2 b has a smallest value.

Moreover, as will be explained in the descriptions of Example 1 later,in the recording medium of this embodiment, the exposure pattern of aresist corresponding to the recording tracks 2 can be obtained by theirradiation with a plurality of electron beams. For example, assumingthat an exposure pattern having a track pitch of 260 nm is written with26 electron beams, and the ratio of the widths of a recording track 2and a non-recording section 4 is two to one, the number of electronbeams used to form the recording tracks is 18. Assuming that a portioncorresponding to the recording section and a portion corresponding tothe connecting section are formed by changing the width of the electronbeam, the width of the portion corresponding to the connecting sectionshould be narrower than the sum of the widths of at least 18 electronbeams, as shown in FIG. 20. Accordingly, the width of the portioncorresponding to the connecting section becomes the sum of 16 electronbeams at maximum. This means that the maximum cross sectional area inthe track width direction of the connecting section 2 b of the magneticrecording medium in this embodiment should be 8/9 or less of the maximumcross sectional area in the track width direction of the recordingsection 2 a.

In this embodiment, the height of the connecting section 2 b measuredfrom the substrate plane is substantially the same as the height H ofthe recording section 2 a, and the size in the track width directiondecreases as the distance from one of the two adjacent recordingsections 2 a increases, and increases as the distance to the otherdecreases, as shown in FIG. 2. However, as in the case of a modificationof this embodiment shown in FIG. 3, the size of the connecting section 2b in the track width direction can be substantially the same as thewidth B of the recording section 2 a, and the height from the substrateplane can decrease as the distance from one of the two adjacentrecording sections 2 a increases, and increases as the distance to theother recording section 2 a decreases. In addition, both the trackstructure shown in FIG. 2 and the track structure shown in FIG. 3 can beprovided.

FIG. 4 shows a cross sectional view obtained by sectioning the magneticrecording medium of this embodiment in a plane in the track widthdirection, i.e., in a direction perpendicular to a track longitudinaldirection. As shown in FIG. 4, in the magnetic recording medium of thisembodiment, a soft magnetic layer 12 is formed on a substrate 10, and aplurality of recording tracks 2 of a magnetic material in a shape ofprojections are formed on the soft magnetic layer 12. A groove isprovided between adjacent recording tracks 2 for magnetically separatingthe adjacent recording tracks 2, the groove serving as a non-recordingsection 4. In this embodiment, a protection layer 14 of a nonmagneticmaterial is filled in the groove serving as the non-recording section 4.As in the case of a second modification of this embodiment shown in aFIG. 5, the protection layer 14 can cover the recording tracks 2.

In the magnetic recording medium of this embodiment thus constituted,each of the connecting sections 2 b arranged in the recording track 2 atregular intervals has a portion having a cross sectional area smallerthan the cross sectional area of each recording section 2 a.Accordingly, even if a recording operation is performed so that amagnetic wall is provided to be slightly shifted from the connectingsection 2 b in the track longitudinal direction, the magnetic wall movestoward the connecting section 2 b since the status of the magnetic wallis more stable when the cross sectional area thereof is smaller. FIG. 6schematically shows an MFM (Magnetic Force Microscope) image in a casewhere different data items are stored in adjacent recording section 2 aof one recording track 2 in this embodiment. In FIG. 6, one of the dateitems “0” and “1” is stored in each white-colored recording section 2 a,and the other is stored in each black-colored recording section 2 a. Ascan be understood from FIG. 6, magnetic walls are fixed to theconnecting sections 2 b. As a result, in the magnetic recording mediumof this embodiment, when magnetic information items are stored in arecording track 2, they are stored in the recording sections 2 a, andthe magnetic walls between adjacent magnetic information items move tothe connecting sections 2 b that are arranged at regular intervals,thereby modifying the recording lengths, which have varied due to theshift in track longitudinal direction of a recording and reproducinghead, to constant lengths.

As a comparative example, FIG. 7 shows an MFM image in a case where dataitems “0” and “1” are alternately stored in one of recording tracks 22of a discrete medium, the recording tracks 22 being separated bynon-recording sections 4, and each recording section 22 extending tohave a constant cross sectional area. As can be understood from FIG. 7,in this comparative example, when a recording operation is performed sothat the magnetic walls are shifted in the track longitudinal direction,the positions of the magnetic walls are not corrected, so that themagnetic walls do not appear at regular intervals.

Accordingly, the S/N ratio of the magnetic recording medium according tothis embodiment is improved compared to the comparative example.

For reference, FIG. 8 schematically shows an MFM image in a case wheredata items “0” and “1” are alternately stored in recording sections 24of a patterned medium which are separated by a nonmagnetic material 26.In this patterned medium, the S/N ratio is not degraded since therecording sections 24 are magnetically separated from each other by thenonmagnetic material 26.

Furthermore, in this embodiment, since the smallest cross sectional areaof each connecting section 2 b of the recording track 2 is not 0, therecording sections 2 a of the recording track 2 are not completelyseparated, thereby preventing a decrease in the volume that can be usedfor the recording. As a result, the signal intensity of the reproducedsignal increases in proportion to the volume compared to a case of apatterned medium having the same recording density. Thus, it is possibleto satisfactorily reproduce the recorded data as shown in FIG. 9, whichshows a reproduction signal in a case where data items “0” and “1” arealternately stored in the recording sections 2 a as shown in FIG. 6. Forreference, FIGS. 10 and 11 show reproduction signals of a patternedmedium in which data items “0” and “1” are alternately recorded inadjacent recording sections, and of a discrete medium of theaforementioned comparative example. As can be understood from FIG. 10,the intensity of the reproduction signal of the patterned medium islower than that of the reproduction signal of the magnetic recordingmedium according to this embodiment shown in FIG. 9. Furthermore, as canbe understood from FIG. 11, the intensity and the interval of thereproduction signals of the discrete medium are not constant compared tothe reproduction signals of the magnetic recording medium according tothis embodiment shown in FIG. 9.

The magnetic recording medium according to this embodiment is mosteffective when the interval between adjacent recording tracks 2 is 200nm or less, with which the magnetic walls in the recording patternbecome unstable. It is preferable that the width of each recordingsection 2 a be 50 to 90% of the track interval, and more preferably, 60%to 80% thereof.

Preferably, the height of each recording track 2 measured from thesurface of the soft magnetic layer 12 shown in FIG. 4 is 100 nm or lessin order to achieve a stable flying height of the recording andreproducing head, but the height of 1 nm or less is not preferable fromthe viewpoint of the separation of magnetism.

Furthermore, it is preferable that the ratio of the smallest crosssectional area of the connecting section 2 b to the smallest crosssectional area of the recording section 2 a be 10% to 90%, morepreferably 20% to 80%, and ideally 50% since if it is too high, themagnetic walls are not stably fixed, and if it is too low, the magneticmaterial volume is impaired, thereby decreasing the signal intensity.

Although it is preferable that both the width and the height of theconnecting section 2 b be smaller than those of the recording section 2a, there is no problem if only one of them is smaller.

In this embodiment, the substrate is ring-shaped having a hole at thecenter thereof, and the material of the substrate can be a metal, analloy or compound thereof, glass, a ceramic material, or an organicmaterial.

An appropriate magnetic material for constituting the recording track isone having great saturation magnetization is and magnetic anisotropy.From this point of view, it is preferable that the magnetic materialcontain at least one material selected from the group consisting of Co,Pt, Sm, Fe, Ni, Cr, Mn, Bi, Al and an alloy thereof. It is particularlypreferable that the material be a Co-group alloy, especially CoPt-,SmCo-, or CoCr-based alloy in which the crystal magnetic anisotropy isgreat, or an ordered alloy such as FePt and CoPt.

There is no limitation on the thickness of the magnetic material butconsidering that a high density recording should be performed, thethickness should preferably be 100 nm or less, more preferably 50 nm orless, and further preferably 20 nm or less. However, a thickness of 0.1nm or less is not preferable since with such a thickness, it isdifficult to form a thin film.

The nonmagnetic material can be a metal, glass, a ceramic material, oran organic material that is not a magnetic material. In the case of ametal, it is particularly preferable that the material contains at leastone metal selected from the group consisting of Cu, Ti, Mo, Al, and Mg,and an alloy thereof, or that the aforementioned materials are stackedto form a multilayer. In the case of a nonmetal, it is preferable thatthe material contain SiO₂ or C.

The material of the protection layer can be substantially the same asthe aforementioned nonmagnetic material, but it is preferable that thedifferences between the projections and depressions on the surface be 30nm or less, and more preferably 10 nm or less in order to restrict theflying height of the recording and reproducing head.

As described above, according to this embodiment, it is possible toimprove the recording and reproducing S/N ratio, the reproduction signalintensity, and the degree of high density recording.

Furthermore, since the non-recording sections 4 of this embodiment areformed of a nonmagnetic material, adjacent recording tracks aremagnetically separated from each other. Accordingly, it is possible towrite to the recording tracks without the negative influence of leakagemagnetic field of the recording and reproducing head.

Moreover, since the smallest area of the connecting sections of arecording track is not 0 in this embodiment, the area of depressedportions is smaller than that of a patterned medium. As a result, theflattening of the medium is easier and the flying height of a recordingand reproducing head can be stabilized at a position relatively low withrespect to the medium.

Although the smallest cross sectional area of the connecting sections 2b is not 0 in this embodiment, it can be 0 in some connecting sections.It is preferable that the ratio of the connecting sections in which thesmallest cross sectional area is 0 to the entire track be 50% or less.In such a case, it is possible to obtain an effect similar to thisembodiment.

Second Embodiment

Next, a magnetic recording medium substrate according to a secondembodiment of the present invention will be described below withreference to FIGS. 12 and 13. FIG. 12 is a plan view of a magneticrecording medium substrate 30 according to this embodiment, and FIG. 13is a sectional view of the magnetic recording medium substrate 30 ofthis embodiment taken along the line A-A shown in FIG. 12.

The magnetic recording medium substrate 30 of this embodiment includesprotruded portions 32 corresponding to recording tracks, and depressedportions 34 for separating adjacent protruded portions. Each protrudedportion 32 includes first portions 32 a corresponding to recordingsections, and connecting sections 32 b for connecting adjacent firstportions 32 a. Pairs each including one first portion 32 a and onesecond portion 32 b are arranged in a track longitudinal direction atregular intervals.

The cross sectional area in a direction perpendicular to the tracklongitudinal direction, i.e., the track width direction, of the secondportion 32 b decreases as the distance from one of the adjacent twofirst portions 32 a increases, and increases as the distance to theother first portion 32 a decreases. Thus, the cross sectional areabecomes the smallest at a substantially central portion of the secondportions 32 b. Furthermore, the greatest cross sectional area in thetrack width direction of the second portion 32 b is adjusted to besubstantially the same as the smallest cross sectional area in the trackwidth direction of the first portion 32 a. That is to say, a secondportion 32 b includes a portion having a smaller cross sectional areathan a first portion 32 a. In this embodiment, the smallest crosssectional area of the second portions 32 b is not “0”. However, asexplained in the descriptions of the first embodiment, the smallestcross sectional area of some second portions can be “0”. In such a case,it is preferable that the ratio of the second portions with the smallestcross sectional area being “0” to the entire second portions be 50% orless.

A magnetic recording medium is formed from the substrate 30 of thisembodiment thus constituted by forming a magnetic film 36 on the surfaceof the substrate 30 by a sputtering method as shown in FIG. 14. At thistime, the magnetic film 36 formed on a protruded portion 32 serves as arecording track, and a depressed portion 34 serves as a non-recordingsection. Thereafter, as shown in FIG. 15, an embedded layer 38 of anonmagnetic material can be formed in the depressed portions 34.Furthermore, as shown in FIG. 16, the embedded layer 38 can cover theprotruded portions 32 serving as the recording tracks. Moreover, asshown in FIG. 17, a protection layer 40 of a nonmagnetic material or alubricant can be formed on the magnetic film 36. The first portion 32 awith the magnetic film 36 corresponds to the recording section of themagnetic recording medium in the first embodiment, and the secondportion 32 b with the magnetic film corresponds to the connectingsection of the magnetic recording medium in the first embodiment. Themagnetic recording medium in this embodiment is called asubstrate-processed magnetic recording medium, and the magneticrecording medium of the first embodiment is called a magneticmaterial-processed magnetic recording medium.

As in the case of the first embodiment shown in FIG. 2, the height ofthe second portion 32 b of this embodiment measured from the bottomsurface of the depressed portion 34 is substantially the same as theheight of the first portion 32 a, and the size in the track widthdirection of the second portion 32 b decreases as the distance from oneof the two adjacent first portions 32 a increases, and increases as thedistance to the other first portion 32 a decreases. However, as in thecase of the modification of the first embodiment shown in FIG. 3, thesize of the second portion 32 b in the track width direction can besubstantially the same as the width of the first portion 32 a, and theheight of the second portion 32 b measured from the bottom surface ofthe depressed portion 34 can decrease as the distance from one of thetwo adjacent first portions 32 a increases, and increase as the distanceto the other first portion 32 a decreases. It is also possible that bothof the aforementioned structures are provided.

As in the case of the first embodiment, the magnetic recording mediummanufactured using the substrate of this embodiment includes a pluralityof recording tracks formed of a magnetic material 36 on a substrate 30,and non-recording sections each separating adjacent recording tracks.Each recording track includes recording sections, in which recordinginformation is stored, and connecting sections each connecting adjacentrecording sections. A pair of a recording section and a connectingsection is disposed at a regular interval in a longitudinal direction ofthe track. One recording section stores a magnetic information itemcorresponding to data “0” or “1”. The cross sectional area in adirection perpendicular to the track longitudinal direction, i.e., thetrack width direction, of the connecting section decreases as thedistance from one of the adjacent recording sections increases, andincreases as the distance to the other recording section decreases.Thus, the cross sectional area becomes the smallest at a substantiallycentral portion of the connecting section. Furthermore, the greatestcross sectional area in the track width direction of the connectingsection is adjusted to be substantially the same as the smallest crosssectional area in the track width direction of the recording section.That is to say, the connecting section includes a portion having asmaller cross sectional area than the recording section.

Accordingly, as in the case of the first embodiment, a magneticrecording medium manufactured using the substrate of this embodimentprovides a good recording and reproducing S/N ratio, and an improvedreproduction signal intensity, and enables a high-density recording.

The magnetic recording medium substrate according to this embodiment ismost effective when the interval between adjacent protruded portions 32is 200 nm or less. It is preferable that the width of the first portion32 a be 50% to 90% of the interval of the protruded portions 32, andmore preferably, 60% to 80% thereof.

As in the case of the first embodiment, it is preferable that the heightof protruded portions 32 measured from the bottom surface of depressedportion 34 be 100 nm or less in order to achieve a stable flying heightof the recording and reproducing head, but the height of 1 nm or less isnot preferable from the viewpoint of the separation of magnetism.

Furthermore, preferably the ratio of the smallest cross sectional areaof the second portion 32 b to the smallest cross sectional area of thefirst portion 32 a is 10% to 90%, more preferably 20% to 80%, andideally 50% since if it is too great, the magnetic walls are not stablyfixed, and if it is too small, the magnetic material area is impaired,thereby decreasing the signal intensity.

Although it is preferable that both the width and the height of thesecond portion 32 b be smaller than those of the first portion 32 a,there is no problem if only one of them is smaller.

In this embodiment, the substrate is ring-shaped having a hole at thecenter thereof, and the material of the substrate can be a metal, analloy or compound thereof, glass, a ceramic material, or an organicmaterial.

Third Embodiment

Next, a magnetic recording and reproducing apparatus according to athird embodiment of the present invention is shown in FIGS. 18 and 19.In a magnetic recording and reproducing apparatus 150 of thisembodiment, a magnetic recording medium according to the firstembodiment or the modification thereof or a magnetic recording mediummanufactured using the substrate according to the second embodiment isprovided.

FIG. 18 is a perspective view schematically showing the structure of amain part of such a magnetic recording and reproducing apparatus.Specifically, a magnetic recording and reproducing apparatus 150according to this embodiment uses a rotary actuator. In this drawing, amagnetic recording medium 200 for longitudinal recording orperpendicular recording is attached to a spindle 152 and is rotated by amotor (not shown), which is responsive to a control signal sent from adriving apparatus control section (not shown), in a direction indicatedby an arrow A. The magnetic recording medium 200 includes a recordinglayer for longitudinal recording or perpendicular recording. In themagnetic recording medium 200, a head slider 153 for recordinginformation in and reproducing information from the magnetic recordingmedium 200 is attached to a tip of a suspension 154 in a thin-filmshape. The head slider 153 includes at a tip thereof a magnetic headincluding a magnetoresistive element as a reproducing element.

When the magnetic recording medium 200 is rotated, the air bearingsurface (ABS) of the head slider 153 is held with a predetermined flyingheight with respect to the surface of the magnetic recording medium 200.

The suspension 154 is connected to one end of an actuator arm 155including a bobbin portion for supporting a driving coil (not shown) andso on. A voice coil motor 156, which is a kind of a linear motor, isprovided to the other end of the actuator arm 155. The voice coil motor156 includes a driving coil (not shown) wound by the bobbin portion ofthe actuator arm 155 and a permanent magnet and an opposite yoke locatedso as to be opposite to each other with the driving coil beingsandwiched therebetween.

The actuator arm 155 is supported by ball bearings (not shown) providedat the upper and lower portions of a fixed spindle 157, and can befreely rotated and slid by the voice coil motor 156.

FIG. 19 is an enlarged perspective view of a portion of the magnetichead assembly extending from the actuator arm 155, which is viewed fromthe disk side. Specifically, a magnetic head assembly 160 includes anactuator arm 155 including, for example, a bobbin portion for supportinga driving coil, and a suspension 154 is connected to one end of theactuator arm 155.

A head slider 153 including any of the aforementioned magnetic heads isattached to the tip of the suspension 154. A reproducing head can alsobe attached. The suspension 154 has lead wires 164 for reading andwriting signals. The lead wires 164 are electrically connected toelectrodes of the magnetic head incorporated into the head slider 153.In the drawing, the reference numeral 165 denotes an electrode pad ofthe magnetic head assembly 160.

In the magnetic recording and reproducing apparatus according to thisembodiment, the cycle of the recording units of the recording andreproducing head is the cycle of the recording section of the recordingtrack of the magnetic recording medium 200. Furthermore, as explained inthe descriptions of the first embodiment, the magnetic walls serving asthe boundaries of recording items exist in the connecting sectionsperiodically arranged in the magnetic recording medium used in themagnetic recording and reproducing apparatus of this embodiment.Accordingly, the S/N ratio at the time of the reading of information isimproved. As a result, in the magnetic recording and reproducingapparatus of this embodiment, the reciprocal of the frequency ofrecorded data is equal to (the number of revolutions of the magneticrecording medium 200)×(the length of a recording track)/(the interval ofadjacent connecting sections).

EXAMPLES

Hereinafter, examples of the present invention will be described.

Example 1

A magnetic recording medium obtained by Example 1 of the presentinvention will be described below. The magnetic recording medium of thisexample is a magnetic material-processed recording medium having adiameter of 2.5 inches manufactured according to the first embodiment.The track pitch thereof is 85 nm, the interval between the recordingsection and the connecting section at the position 14 mm from the centerof the recording medium having a diameter of 2.5 inches is 12 nm. Thenumber of revolutions of medium in the magnetic recording apparatus, towhich the recording medium of Example 1 is mounted, is set to be 4,200rpm, and the recording frequency is set to be 500 MHz. As a result, thearrangement cycle of the recording sections and the connecting sectionsat the innermost circumference, i.e., the radius position of 14 mm is 12nm, which corresponds to 2 MFCI (Mega Flux Changes per Inches).

The magnetic recording medium of this example is manufactured by animprinting method using an imprint stamper. A method of manufacturing amagnetic recording medium of this example will be described below withreference to FIGS. 21A to 27D.

First, a method of manufacturing an imprint stamper will be describedwith reference to FIGS. 21A to 23.

As shown in FIG. 21A, a resist is diluted two times with anisole,filtered by a membrane filter having a thickness of 0.2 pm, and spincoated on a silicon substrate 42. Immediately after this, the workpieceis pre-baked at a temperature of 200° C. for three minutes, therebyobtaining a resist 44 having thickness of 0.1 μm.

Thereafter, a pattern of the recording tracks 2 and the non-recordingsections 4 shown in FIG. 1 is exposed by using a lithography machine, bywhich the pattern is transferred to the resist 44 (FIG. 21B). Theexposure pattern at this time is shown in FIG. 22. In FIG. 22, ablackened portion is a trace of an electron beam radiation. An exposurepattern including portions 44 _(2a) corresponding to the recordingsections 2 a and portions 44 _(2b) corresponding to the connectingsections 2 b is formed by irradiating the workpiece with a plurality ofelectron beams. FIG. 22 shows an exposure pattern in a case where theshape of a recording track 2 is as shown in FIG. 2. When the shape of arecording track 2 is as shown in FIG. 3, an exposure pattern can beobtained by differentiating the exposure intensities between theportions 44 _(2a) corresponding to the recording sections 2 a and theportions 44 _(2b) corresponding to the connecting sections 2 b, as shownin FIG. 23.

After the exposure, the substrate 42 is immersed in a developingsolution to develop it, then in a rinse agent, and blow dried, therebyobtaining a resist master including a resist pattern 44 a (FIG. 21C).

Next, as shown in FIG. 21D, a thin conductive film 46 is formed on theresist master by a sputtering method. Pure nickel is used as a target,and the sputtering is performed in a chamber, which has once beenvacuumed until 8×10⁻³ Pa and then filled with argon gas until a pressurereaches 1 Pa, with a DC power of 400 W in order to obtain the conductivefilm 46.

Thereafter, the resist master with the conductive film 46 iselectroformed, thereby forming an electroformed film 48 (FIG. 21E).

Then, the electroformed film 48 is removed from the resist master,thereby obtaining a stamper 50 including the conductive film 46, theelectroformed film 48, and a resist residue (FIG. 21F). Subsequently,the resist residue is removed by an oxygen plasma ashing method (FIG.21G). As a result, a further stamper 50 including the conductive film 46and the electroformed film 48 is obtained. Thereafter, an unnecessaryportion of the stamper obtained is punched out by using a metal blade,thereby obtaining an imprint stamper.

Then, the stamper 50 is ultrasonic cleaned with acetone, and is immersedfor 30 minutes in a solution obtained by diluting fluoroalkylsilane(CF₃(CF₂)₇CH₂CH₂Si(OMe)₃) (GE Toshiba Silicones Co., Ltd., ProductNumber TSL8233) in ethanol to a concentration of 5% in order to improvethe mold-releasing property. Thereafter, the solution remaining on theworkpiece is blown with a blower, and the workpiece is annealed at atemperature of 120° C. for one hour.

The stamper 50 can be obtained by arranging, in grooves 47 a of a resistpattern 47 as shown in FIG. 24, a diblock polymer 49 forming asea-island structure with a phase separation similar to that of PS-PMMA(Polystyrene-Polymethylmethacrylate), and by performing an etchingoperation using it as a mask to form a pattern on the stamper. Althoughthe islands are separated in the arrangement of polymer according to thephase separation, it is possible to form a pattern 50 a shown in FIG. 25by connecting adjacent islands during the etching step.

Next, a method of manufacturing a magnetic material-processed magneticrecording medium using the stamper 50 will be described below. As shownin FIG. 26A, a substrate obtained by forming a magnetic film 52 ofCoCrPt on a substrate to be processed 31 of ring-shaped glass havingdiameter of 2.5 inches is prepared, a protection layer 53 of carbon isformed on the magnetic film 52, and a resist is spin coated on theprotection layer 53 to have a thickness of 100 nm, thereby forming aresist film 54. Subsequently, position alignment of the stamper 50 withrespect to the substrate to be processed 51 is performed (FIG. 26B), andthe stamper 50 is pressed, thereby transferring the pattern of thestamper 50 to the resist film 54 (FIG. 26C). Ultraviolet light isirradiated on the resist film 54, on which the pattern had beentransferred, to harden it, and a heat treatment is performed.

Then, oxygen RIE is performed on the resist film 54 of the substrate, onwhich the imprinting had been performed as described above, using ICP(Inductively Coupled Plasma) etching equipment at an etching pressure of2 mTorr, thereby forming a resist pattern 54 a (FIG. 26D).

Subsequently, the protection layer 53 and the magnetic film 52 areetched by performing Ar ion milling using the resist pattern 54 a as amask, thereby forming a discrete magnetic film 52 a, on which theprotection layer 53 a is formed (FIG. 27A).

After the magnetic film 52 a is formed, the resist pattern 54 a havingbeen used as an etching mask is removed by performing oxygen RIE,thereby exposing the protection layer 53 a. At this time, the height ofthe magnetic film 52 a from the substrate 51 is from 5 nm to 50 nm. Theprotection layer 53 a can be removed at the same time as the resistpattern 54 a to expose the magnetic film 52 a.

When the height of the magnetic film 52 a is 10 nm or more, anonmagnetic material layer 56 is deposited so as to cover the magneticfilm 52 a and the protection layer 53 a as shown in FIG. 27B. Thenonmagnetic material can be SiO₂, C, Cu, Al, Ti or the like.

Subsequently, the magnetic material layer 56 is etched back to exposethe surface of the protection layer 53 a or the magnetic film 52 a (FIG.27C). Thereafter, as shown in FIG. 27D, a protection layer 58 of, forexample, carbon is deposited on the entire surface of the workpiece.Then, abnormal projections are removed with tape varnish, and alubricant is applied to have a thickness of 1 nm by a dipping method,thereby completing a magnetic material-processed magnetic recordingmedium.

The magnetic recording medium of this example has a servo having aconcentric circular shape, an address, a preamble, recording tracks, andnon-recording sections.

Example 2

Next, a magnetic recording medium according to Example 2 of the presentinvention will be described below. The magnetic recording medium of thisexample is a substrate-processed recording medium manufactured by usinga magnetic recording medium substrate according to the secondembodiment, and has the same size as recording medium according toExample 1.

The substrate of the magnetic recording medium according to this exampleis manufactured by an imprinting method. A method of manufacturing amagnetic recording medium according to this example will be describedbelow with reference to FIGS. 28A to 29D.

A glass substrate 61 of a disk shape is prepared (FIG. 28A), on which anSOG layer 62 is formed by spin coating SOG (Spin-On-Glass). Animprinting operation is performed on the glass substrate 61 by using thestamper 50 of Example 1, thereby transferring a pattern of the SOG layer62 (FIGS. 28A and 28B). Instead of SOG, an alcohol dispersion containingAl₂O₃ or TiO₂ can be used.

Next, a reactive etching treatment is performed on the workpiece using afluorine containing gas (for example, SF₆) to remove the residue of SOGremaining at the bottom of the depressed portions of the transferredpattern, thereby forming an SOG pattern 62 a (FIG. 28C). Subsequently,an ion milling treatment using Ar is performed using the SOG pattern 62a as a mask to process the glass substrate 61, thereby obtaining aprocessed substrate 61 a (FIG. 28D).

Next, as shown in FIG. 29A, the SOG pattern 62 a on the processedsubstrate 61 a is removed using SF₆. Thereafter, the sputteringdeposition of CoCrPt is performed on the processed substrate 61 a toform a magnetic film 63, and the projections and depressions of thesubstrate 61 a are covered with a nonmagnetic film 64 of a nonmagneticmaterial such as SiO₂, C, Cu, Al, Ti or the like using a sputteringmethod (FIG. 29B).

Then, as shown in FIG. 29C, the nonmagnetic film 64 is etched back toexpose the magnetic film 63 on the protruded portions of the substrate61 a. Thereafter, a protection layer 65 of carbon is deposited by usinga sputtering method (FIG. 29D). Then, abnormal projections are removedwith tape varnish, and a lubricant is applied, thereby completing amagnetic recording medium of this example.

Example 3

Next, a method of manufacturing a magnetic recording medium according toExample 3 of the present invention will be described below withreference to FIGS. 30A to 31D. In the manufacturing method of thisexample, a mask for processing a magnetic material is formed by using adiblock polymer. A magnetic recording medium manufactured by thismanufacturing method becomes a magnetic material-processed recordingmedium of the first embodiment.

As shown in FIG. 30A, a magnetic film 72 is formed on a substrate 71,and a resist pattern 74 including grooves in a track shape having aconstant cross sectional area and a width ranging from 20 nm to 150 nmis formed on the magnetic film 72.

Subsequently, a diblock polymer 75 of PS-PMMA(Polystyrene-Polymethylmethacrylate) dissolved in PGMEA (PlopyleneGlycol Monomethylether Acetate) is applied to the grooves in track shapeof the resist pattern 72 by a spin coating method (FIG. 30B).Thereafter, an annealing treatment is performed on the workpiece at atemperature of 180° C. in an N₂ atmosphere containing H₂ at aconcentration of 1 to 3%. After this treatment, the diblock polymer 74has a sea-island structure in which islands 74 a of PMMA are arranged atregular intervals in a sea 74 b of PS (Polystyrene) (FIG. 30C).

Subsequently, a reactive ion etching using O₂ was performed. Since theetching rate of the PS 74 b is different from that of the PMMA 74 a,only the portions corresponding to the PMMA 74 a are etched to formholes 75, as shown in FIG. 31A. Subsequently, as shown in FIG. 31B, theholes 75 are filled with SOG 76.

Then, as shown in FIG. 31C, reactive ion etching using O₂ is performedusing the SOG 76 as a mask, thereby etching and removing the resistpattern 74 and the PS 74 b in the portions where the SOG 76 are notformed. Subsequently, the magnetic film 72 is patterned with Ar gasusing the remaining SOG 76 and the PS 74 b located underneath as masks,and then the SOG 76 and the PS 74 b located underneath are removed toobtain a patterned magnetic film 72 a shown in FIG. 31C. Thereafter, asexplained in the descriptions of Example 1, a nonmagnetic layer and aprotection layer are formed to complete the magnetic recording medium.

Although the tracks of this example are formed by an imprinting method,a lithography technique using electron beams can also be used.

It is possible to form a pattern in which the sea and the islands arereversed from those of this example by changing the composition ratiobetween PS and PMMA in the diblock polymer. In such a case, the portionsother than the islands are used as tracks.

In contrast to the aforementioned examples, magnetic recording mediumsare manufactured in accordance with the following Comparative Examples 1and 2.

As Comparative Example 1, a discrete magnetic recording medium ismanufactured, which has the same size as Example 1 except for thetracks, the width of which is constant. As Comparative Example 2, apatterned medium is manufactured in which the size and the recordingdensity are the same as those of Example 1.

A read/write (R/W) test was performed by mounting the magnetic recordingmedia according to Examples 1 to 3 and the recording media according toComparative Examples 1 and 2 on the magnetic recording and reproducingapparatus according to the third embodiment, writing signals using amagnetic monopole head as a write head, and reading signals using a GMRhead as a reproducing head. As the measurement condition, the magneticrecording medium was rotated at 4,200 rpm at the radius position of 14mm from the center. The outputs of 2 MFCI signals are shown below. Withrespect to the medium S/N ratio (S/Nm), S value is a half value of a ppvalue (difference between the positive and negative greatest values) atthe time of one magnetization reversal of a solitary wave at 10 kFCI,and Nm value is a rms (root mean square) value of noise at 2 MFCI. Inaddition, the head flying property at the medium surface was alsoevaluated using an AE sensor.

The obtained results are shown in the following table.

TABLE 1 Output (mV) S/Nm (dB) Flying Stability Example 1 1.05 24.9Excellent Example 2 1.08 24.0 Excellent Example 3 0.74 25.3 GoodComparative 1.10 21.9 Excellent Example 1 Comparative 0.58 25.6 FairExample 2

From the above comparison results, it can be understood that the outputsof the magnetic recording media according to Examples 1 to 3 are greatercompared to the output of a patterned medium according to theComparative Example 2, and the S/N ratios thereof are better compared toa discrete medium according to Comparative Example 1.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcepts as defined by the appended claims and their equivalents.

1. A magnetic recording medium substrate comprising: a plurality ofprotruded portions formed on a substrate, each protruded portion beingin a track shape; and depressed portions formed on the substrate, eachdepressed portion separating adjacent protruded portions, each protrudedportion including a plurality of first portions and second portions forconnecting the first portions adjacent thereto in a track longitudinaldirection, and each second portion having a cross-sectional area in atrack width direction that is smaller than a cross-sectional area in atrack width direction of adjacent first portions.
 2. The magneticrecording medium substrate according to claim 1, wherein thecross-sectional area in the track width direction of each second portionhas a smallest value.
 3. The magnetic recording medium substrateaccording to claim 2, wherein the cross-sectional area in the trackwidth direction of each second portion decreases as a distance from oneof the two adjacent first portions increases until the cross-sectionalarea reaches the smallest value, and then increases as a distance to theother first portion decreases.
 4. The magnetic recording mediumsubstrate according to claim 1, wherein pairs each including one firstportion and one second portion are periodically arranged in a tracklongitudinal direction.
 5. The magnetic recording medium substrateaccording to claim 1, wherein a size in the track width direction of thesecond portion is smaller than a size in the track width direction ofthe first portion.
 6. The magnetic recording medium substrate accordingto claim 1, wherein a height of the second portion is smaller than aheight of the first portion.
 7. The magnetic recording medium substrateaccording to claim 1, wherein a smallest cross-sectional area in thetrack width direction of the second portion is greater than
 0. 8. Amagnetic recording medium comprising: a magnetic recording mediumsubstrate according to claim 1; and a magnetic film formed on themagnetic recording medium substrate.